The present invention relates to a conformable, heat-resistant, paintable acrylic-based adhesive tape. More particularly, the present invention relates to a two-sided acrylic-based adhesive tape having a conformable liner and a method of applying the tape to a substrate, where the tape can conform to the curves of the substrate and withstand environmental conditions encountered in automotive, appliance, and other commercial paint processes without degradation or a reduction in adhesive properties of the tape.
Acrylic pressure sensitive adhesive tapes are widely used in the automotive and appliance industry to bond a wide variety of substrate materials, and in particular, the application of painted exterior automotive body side moldings, sub-assemblies or trim parts. A common method of application is to use an acrylic attachment tape comprised of a foam core which adheres the substrate materials to the vehicle or appliance. However, a disadvantage of such foam core tapes is that they cannot withstand exposure to a paint bake cycle in which the part is painted and subsequently exposed to high temperatures in a paint oven to cure the painted part. For example, the foam core loses compressibility after the introduction of paint, thereby reducing the ability of the tape to sufficiently wet-out to the mating surface. In addition, the foam core may also break down as entrapped air in the foam expands at the elevated temperatures encountered in the bake cycle, rupturing the foam""s cell structure, which also impedes wet-out and structural strength. Expanded gas can also collect at the tape-surface interface where it interferes with surface wet-out and bond strength.
In order to avoid the degradation of foam core acrylic tapes, the use of a separate masking tape has been employed which is applied to the part prior to the paint bake cycle in the area of the part which is to receive the foam core acrylic attachment tape to prevent that area from receiving paint. The masking tape is then removed after the paint bake cycle and the attachment tape is applied. However, the use of the masking tape adds additional steps and materials to the manufacturing process, which is both time-consuming and costly.
In order to avoid this extra step, the use of adhesive tapes which are heat-resistant have been developed. These adhesive tapes comprise a solid acrylic-based carrier and a heat resistant liner and can be attached to a substrate such as an automotive part and exposed to elevated temperatures without being subject to degradation. However, a disadvantage of such tapes is that they must be die cut for many applications in order to cover parts that are curved, such as wheel flares. The process of die cutting the tape to conform to shaped substrates requires the use of excess tape and adds additional steps to the manufacturing process which are time-consuming and costly.
Thus, there is a need in the art for an adhesive tape and liner construction which is capable of conforming to the substrate to which it is attached. There is also a need in the art for a tape and liner construction which is not adversely affected when exposed to paint, primers, and elevated temperatures such as those encountered in automotive, appliance, and other commercial painting processes.
The present invention meets that need by providing a conformable, heat-resistant tape including a solid core acrylic-based pressure sensitive adhesive and a heat-resistant liner adhered thereto. The liner is conformable and provides the tape with flexibility to conform to the shape of the substrate to which it is attached, remaining in intimate contact with the tape during paint processing. This eliminates the need to die cut the tape, thereby reducing the amount of tape needed for a particular application and the time and labor involved. The liner is also paintable and protects the tape from degradation resulting from exposure to paints and primers encountered during paint processing.
The conformable tape withstands temperatures up to about 300xc2x0 F. (150xc2x0 C.), and eliminates both the need for a separate masking and the need for die cutting when used in the application of paintable automotive part, appliance trim or subassembly parts, and other painted substrates.
According to one aspect of the present invention, a conformable, heat-resistant two-sided acrylic-based tape is provided comprising a solid acrylic-based carrier, a prepolymerized acrylic-based pressure sensitive adhesive on both sides of the carrier, and a conformable, heat-resistant liner adhered to at least one side of the adhesives on the carrier. By conformable, it is meant that the liner conforms to the surface of the substrate to which it is adhered without separating from the tape, and that it expands or contracts with the tape when exposed to the temperatures encountered in a paint bake cycle. To fulfill the requirements of conformability for the present invention, the tape construction must be able to conform to a minimum of a 2-inch radius for a 1-inch wide tape and a 1-inch radius for a 0.5 inch-wide tape.
By xe2x80x9csolidxe2x80x9d carrier, it is meant that the carrier has substantially no gaseous cells (however, the carrier may include microspheres). The carrier or core may be comprised of a single carrier or adhesive material, or a laminate comprising layers of similar or dissimilar carrier or adhesive materials. Thus, the solid carrier is not cellular and will not absorb paint, nor will any gases entrapped in the tape core result in expansion upon exposure to elevated temperatures.
The conformable, heat-resistant tape can withstand temperatures up to about 300xc2x0 F. (150xc2x0 C.) without degradation of the acrylic-based adhesive or liner, and without reducing the bonding properties of the acrylic-based adhesive. The conformable tape is also paintable. By paintable, it is meant that the conformable tape can withstand exposure to paints or primers used in a paint bake cycle without any adverse affects, i.e., without degradation of the acrylic-based adhesive or liner, and without reducing the bonding properties of the acrylic-based adhesive. By xe2x80x9cpaint bake cyclexe2x80x9d, it is meant a process in which the conformable tape is preferably adhered to a substrate such as an automotive, appliance, or other commercial part, primed, painted, and then passed through a paint bake oven which is used to cure the painted parts. The oven temperatures typically range from about 200xc2x0 F. to 300xc2x0 F. (80xc2x0 C. to 150xc2x0 C.) and cure times range from 25 minutes to 2 hours.
The conformable, heat-resistant tape preferably has a peel strength of at least 20 N/cm to the painted substrate after being processed through a paint bake cycle.
Preferably, the tape has a thickness of about 0.5 to 2.0 mm.
The conformable, heat resistant liner is preferably comprised of a polyvinyl chloride-based material. The liner maintains in intimate contact with the tape during paint processing, and expands or contracts with the tape during the process. The liner may be processed through a paint bake cycle without distortion or buckling and functions to protect the acrylic-based adhesive from exposure to solvents contained in paints or primers used during paint processing which could degrade the adhesive.
The conformable, heat-resistant tape of the present invention may be used in a variety of ways. The tape can be adhered to a substrate by adhering at least one side of the two-sided tape to at least one area of a substrate. The conformable, heat-resistant liner on the other side of the tape preferably faces outward. The substrate with the tape adhered thereon may then be painted and exposed to temperatures up to 300xc2x0 F. (150xc2x0 C.) to cure and dry the paint. Preferred substrate materials include wood, metal, glass, thermoplastic olefins, acrylonitrile-butadiene styrene, and polyvinyl chloride-based materials.
In use, the conformable heat resistant tape is preferably adhered to a substrate such as an automotive, appliance, or subassembly trim or part and then passed through a paint bake cycle such that the substrate is painted and/or exposed to heat curing or heat processing operations with the tape adhered to its surface. After the paint bake cycle, the conformable, heat-resistant liner may then be removed to expose the adhesive on the other side of the tape such that the painted part may be adhered to a second substrate such as the side of a vehicle or the body of an appliance.
It should be appreciated that the conformable, heat resistant tape of the present invention may also be used in applications where heat resistance is not required. Such applications include curved mutton bars for windows, curved sheet metal-works used in the HVAC industry, and curved assemblies used in the electronics industry.
Accordingly, it is a feature of the present invention to provide a conformable, heat-resistant, paintable acrylic-based adhesive tape including an acrylic-based adhesive and a conformable, heat resistant liner which may be adhered to a substrate and exposed to paint and elevated temperatures such as those encountered in a paint bake cycle without degradation of the tape or liner. Other features and advantages of the invention will be apparent from the following description, the accompanying drawings, and the appended claims.